Packaging systems that form, fill and seal containers such as thermoplastic bottles and bags enjoy widespread commercial acceptance through ease of operation and reduced labor costs. A container of this type is formed of thermoplastic material, filled with the desired substance, and then sealed in one continuous operation. Generally, these containers are hermetically sealed after the container contents are introduced into the lower portion by pressing together the upper portion of the plastic container which is still soft and sealable. Such a packaging system obviates the need for costly auxiliary equipment to clean and handle empty containers, fill the containers, and seal the containers. The system is particularly desirable where a sterilized fluid is to be sealed within the container and thereafter maintained in a sterile condition.
However, some means must be provided to open the container and obtain access to the material within the container. In medical applications it is desirable to use a cannula or a spike to draw off liquid, e.g., sterile saline, in the container. Such use requires a piercable membrane on the container and preferably also means to seal with the cannula or spike. Thermoplastic molding including the form, fill and seal method can be used to make such a membrane as a unitary part of the container. However the system tolerances required increase the cost of the container or package ultimately produced. Some of the problems encountered are control of the thickness of the membrane, and provision of a convenient location on the container for molding the membrane and the subsequent piercing of the molded membrane. While the membrane can be conveniently pierced when located along the longitudinal axis of the container, such a location usually entails placing a parting line across the surface of the membrane. Such a parting line can interfere with piercing and sealing of the cannula with the membrane unless special precautions are taken.
It would be desirble to produce a container which avoids the shortcomings of the prior art containers and presents a pierceable membrane in a convenient, predetermined location. It would also be desirable if that membrane could be pierced by a cannula which would then seal with the container while in place. It would be further desirable if such a container can be produced by efficient production methods. The present invention meets these desires.